Prediction of Wind Turbine Noise and Validation against Experiment

A semi-empirical prediction method for trailing edge noise is applied to calculate the noise from two modern large wind turbines. The prediction code only needs the blade geometry and the turbine operating conditions as input. Using detailed acoustic array and directivity measurements, a thorough validation of the predictions is carried out. The predicted noise source distribution in the rotor plane (as a function of frequency and observer position) shows the same characteristics as in the experiments: due to trailing edge noise directivity and convective amplification, practically all noise (emitted to the ground) is produced during the downward movement of the blades, causing an amplitude modulation of broadband aerodynamic blade noise at the blade passing frequency (‘swish’). Good agreement is also found between the measured and predicted spectra, in terms of levels and spectral shape. For both turbines, the deviation between predicted and measured overall sound levels (as a function of rotor power) is less than 1–2 dB, which is smaller than the scatter in the experimental data. Using a smoothed analytical trailing edge noise directivity function, the turbine noise directivity is predicted within 1–2 dB, and the swish amplitude in different directions within 1 dB. This semi-empirical directivity function shows similar characteristics as the theoretical directivity function for a flat plate, except for regions close to the plane of the blade. The validated prediction code is then applied to calculate noise footprints of the wind turbine as a function of rotor azimuth. These footprints show that for cross-wind directions the average level is lower than in the up- and downwind directions, but the variation in level is larger. Even at large distance, swish amplitudes up to 5 dB can be expected for cross-wind directions.

[1]  J.,et al.  Sound and Sources of Sound , 2005 .

[2]  Gianfranco Guidati,et al.  Simulation and measurement of inflow-turbulence noise on airfoils , 1997 .

[3]  Thomas F. Brooks,et al.  Airfoil self-noise and prediction , 1989 .

[4]  Stewart A. L. Glegg,et al.  Using RANS Calculations of Turbulent Kinetic Energy to Provide Predictions of Trailing Edge Noise , 2008 .

[5]  Thierry Maeder,et al.  Reduction of Wind Turbine Noise using Optimized Airfoils and Trailing-Edge Serrations , 2008 .

[6]  D. E. Davies,et al.  Array signal processing , 1983 .

[7]  Harvey H. Hubbard,et al.  Aeroacoustics of large wind turbines , 1991 .

[8]  F. Fahy,et al.  Mechanics of flow-induced sound and vibration , 1989 .

[9]  Richard D. Sandberg,et al.  Direct numerical simulation of turbulent flow past a trailing edge and the associated noise generation , 2008, Journal of Fluid Mechanics.

[10]  M. S. Howe.  A review of the theory of trailing edge noise , 1978 .

[11]  Gianfranco Guidati,et al.  Prediction of Turbulent Inflow and Trailing-Edge Noise for Wind Turbines , 2005 .

[12]  Martin Lowson,et al.  Theory and experiment for wind turbine noise , 1994 .

[13]  A. Debruijn,et al.  Determination of the acoustic source power levels of wind turbines , 1984 .

[14]  Gianfranco Guidati,et al.  Comparison of measured and predicted airfoil self-noise with application to wind turbine noise reduction , 1997 .

[15]  Paul G. Migliore,et al.  Semi-Empirical Aeroacoustic Noise Prediction Code for Wind Turbines , 2004 .

[16]  M. S. Howe.  Edge-source acoustic Green's function for an airfoil of arbitrary chord, with application to trailing-edge noise , 2001 .

[17]  Siegfried Wagner,et al.  Prediction and reduction of wind turbine noise - An overview of research activities in Europe , 2000 .

[18]  Thomas J. R. Hughes,et al.  Computation of trailing-edge noise due to turbulent flow over an airfoil , 2004 .

[19]  F. W. Grosveld,et al.  Prediction of broadband noise from large horizontal axis wind turbine generators , 1984 .

[20]  G. P. van den Berg,et al.  Effects of the wind profile at night on wind turbine sound , 2004 .

[21]  Frits van den Berg,et al.  Project WINDFARMperception: Visual and acoustic impact of wind turbine farms on residents. Final report, FP6-2005 , 2008 .

[22]  Stewart A. L. Glegg,et al.  The prediction of broadband noise from wind turbines , 1987 .

[23]  Michel Roger,et al.  Back-scattering correction and further extensions of amiet's trailing-edge noise model. Part 1: theory , 2005 .

[24]  Ewald Krämer,et al.  Design and Wind-Tunnel Verification of Low-Noise Airfoils for Wind Turbines , 2006 .

[25]  Michel Roger,et al.  Competing Broadband Noise Mechanisms in Low-Speed Axial Fans , 2004 .

[26]  S. Oerlemans.  Prediction of wind turbine noise and comparison with experiment , 2007 .

[27]  Pieter Sijtsma,et al.  Location and quantification of noise sources on a wind turbine , 2007 .

[28]  Pieter Sijtsma,et al.  Location of rotating sources by phased array measurements , 2001 .

[29]  Thomas F. Brooks,et al.  Rotor Broadband Noise Prediction with Comparison to Model Data , 2001 .

[30]  Wen Zhong Shen,et al.  Prediction and Reduction of Noise from a 2.3 MW Wind Turbine , 2007 .

[31]  R. H. Schlinker,et al.  Helicopter rotor trailing edge noise , 1981 .

[32]  Michaela Herr,et al.  Experimental investigations in low-noise trailing-edge design , 2004 .

[33]  Martin Lowson,et al.  Wind turbine noise: analysis of results from a new measurement technique , 1998 .

[34]  Jens Nørkær Sørensen,et al.  Modeling of Aerodynamically Generated Noise From Wind Turbines , 2005 .

[35]  Adams,et al.  Research into aerodynamic modulation of wind turbine noise:final report , 2007 .

[36]  J. Williams,et al.  Aerodynamic sound generation by turbulent flow in the vicinity of a scattering half plane , 1970, Journal of Fluid Mechanics.

[37]  M. Drela.  XFOIL: An Analysis and Design System for Low Reynolds Number Airfoils , 1989 .

[38]  Martin R. Fink.  Noise Component Method for Airframe Noise , 1979 .

[39]  Thomas F. Brooks,et al.  Effects of Angle of Attack and Velocity on Trailing Edge Noise , 2004 .

[40]  C. Burrus,et al.  Array Signal Processing , 1989 .

[41]  Stefan Oerlemans,et al.  Aeroacoustic wind tunnel tests of wind turbine arfoils , 2004 .

[42]  S. Oerlemans,et al.  Quantification of Airframe Noise Using Microphone Arrays in Open and Closed wind Tunnels , 2007 .